This invention relates to ladder construction, and in particular, to a ladder having an integrally molded rung flange mounted along the web of the ladder side rails.
In ladders, particularly all plastic extension ladders with rungs and side rails made by the pultrusion process, the rungs have been mounted in the ladder webs by assemblies of individual plastic parts. An illustrative example of such assemblies and ladder construction method is shown and described in the U.S. Pat. No. 3,426,867 to Berger. While this has produced a satisfactory ladder, the assembly of the various parts is a relatively time consuming and expensive procedure.
It has been suggested to mold rung receiving bosses integral with the web or side piece of the spaced side rails, as disclosed in Merritt et al, U.S. Pat. No. 3,481,428. Such a construction is difficult to accomplish and precludes the use of a different material for the rung brackets from the material of which the rails are made. In addition, ladders constructed in accordance with Merritt have a web that is reinforced only on one broad side.
The invention disclosed hereinafter overcomes the deficiencies of the prior art by providing a structure and method of manufacturing a rung flange so that the flange becomes an integral part of the side rails. Ladder construction is simplified and rung insertion and attachment is easily accomplished.
One of the objects of this invention is to provide a ladder and method of making it which is more economical and at the same time produces a stronger construction than that of ladders of the same general type known heretofore.
Another object of this invention is to provide a rung flange which may be molded and integrally attached to the side rail of a ladder.
Other objects will become apparent to those skilled in the art in light of the following description and accompanying drawings.